Investigating the inhibitory effect of nettle (Urtica dioica L.) essential oil and Pickering nanoemulsion on some pathogenic bacteria inoculated into pizza cheese.

Abstract

The aim of the present research was to evaluate the effect of Urtica dioica L. (nettle) essential oil (in the forms of Pickering nanoemulsion (NEO) and free (EO)) on microbial, chemical and sensory changes of pizza cheese stored at 4 °C for 12 days. For this purpose, Escherichia coli and Listeria monocytogenes were inoculated into pizza cheese. In all tests, the control group had the lowest score after 12 days of storage. In the antimicrobial assay test in different treatments, NEO4% treatment decreased the growth of E.coli from 4 (0th day) to 3.3 log CFU/g (12th day) and the growth of L. monocytogenes from 3.8 (0th day) to 3.1 log CFU/g (12th day). The minimum inhibitory concentration (MIC) of NEO and EO for E.coli and L. monocytogenes was 0.62 ± 0.01 mg/mL. Additionally, the minimum bactericidal concentration (MBC) of EO and NEO for E. coli was 25 ± 0.1 mg/mL, and for L. monocytogenes was 1.25 ± 0.1 mg/mL. At day 12, almost all treatments (free form and nano) had relatively similar pH. In our study, the minimum and maximum value of DPPH was detected in the treatment of NEO1% (31.25 ± 1.50 %) and BHT200 (96.40 ± 2.5 %), respectively. Also, on the 12th day of the test, the NEO treatment obtained the highest score in all sensory tests (appearance & color, body & texture, odor and overall acceptability). According to the findings of the present study, Pickering emulsion form of nettle EO increases the storage period of pizza cheese.